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• How to convert a Stream on the fly with FFMpegCore ?

  18 octobre 2023, par Adrian

  For a school project, I need to stream videos that I get from torrents while they are downloading on the server.
When the video is a .mp4 file, there's no problem, but I must also be able to stream .mkv files, and for that I need to convert them into .mp4 before sending them to the client, and I can't find a way to convert my Stream that I get from MonoTorrents with FFMpegCore into a Stream that I can send to my client.

  


  Here is the code I wrote to simply download and stream my torrent :

  


  var cEngine = new ClientEngine();

var manager = await cEngine.AddStreamingAsync(GenerateMagnet(torrent), ) ?? throw new Exception("An error occurred while creating the torrent manager");

await manager.StartAsync();
await manager.WaitForMetadataAsync();

var videoFile = manager.Files.OrderByDescending(f => f.Length).FirstOrDefault();
if (videoFile == null)
    return Results.NotFound();

var stream = await manager.StreamProvider!.CreateStreamAsync(videoFile, true);
return Results.File(stream, contentType: "video/mp4", fileDownloadName: manager.Name, enableRangeProcessing: true);


  


  I saw that the most common way to convert videos is by using ffmpeg. .NET has a package called FFMpefCore that is a wrapper for ffmpeg.

  


  To my previous code, I would add right before the return :

  


  if (!videoFile.Path.EndsWith(".mp4"))
{
    var outputStream = new MemoryStream();
    FFMpegArguments
        .FromPipeInput(new StreamPipeSource(stream), options =>
        {
            options.ForceFormat("mp4");
        })
        .OutputToPipe(new StreamPipeSink(outputStream))
        .ProcessAsynchronously();
    return Results.File(outputStream, contentType: "video/mp4", fileDownloadName: manager.Name, enableRangeProcessing: true);
}


  


  I unfortunately can't get a "live" Stream to send to my client.

  


• Find video resolution and video duration of remote mediafile

  22 février 2012, par osgx

  I want to write an program which can find some metainformation of mediafile. I'm interested in popular video formats, such as avi, mkv, mp4, mov (may be other popular too). I want basically to get :

  • Video size (720, 1080, 360 etc)
  • Total runtime of video (may be not very exact)
  • Number of audio streams
  • Name of video codec
  • Name of audio codec

  There is already the mediainfo, but in my program I want to get information about remote file, which may be accessed via ftp, http, samba ; or even torrent (there are some torrent solutions, which allows to read not-yet downloaded file).

  MediaInfo library have no support of samba (smb ://) and mkv format (for runtime).

  Also, I want to know, how much data should be downloaded to get this information. I want not to download full videofile because I have no enough disk space.

  Is this information in the first 1 or 10 or 100 KiloBytes of the file ? Is it at predictable offset if I know the container name and total file size ?

  PS : Platform is Linux, Language is C/C++

• avformat/matroskadec : Check min_luminance more thoroughly

  16 février 2021, par Andreas Rheinhardt

  avformat/matroskadec : Check min_luminance more thoroughly
  In the absence of an explicitly coded minimal luminance, the current
  
  code inferred it to be -1, an invalid value. Yet it did not check the
  
  value lateron at all, so that if a valid maximum luminance is
  
  encountered, but no minimal luminance, an invalid minimal luminance of
  
   1 is exported. If an minimal luminance element with a negative value is
  
  present, it is exported, too. This can be simply fixed by adding a check
  
  for the value of the element.
  Yet given that a minimal luminance of zero Cd/m² is legal and can be
  
  coded with a length of zero, we must not use a fake default value to
  
  find out whether the element is present or not. Therefore this patch
  
  uses an explicit counter for it.
  While just at it, also check for max_luminance > min_luminance.
  Reviewed-by : Ridley Combs <rcombs@rcombs.me>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskadec.c